Hydraulic tappet



Sept. 1, 1964 M, v, DADD 3,146,767

' HYDRAULIC TAPPET Filed May 16, 1963 INVENTOR. MORE/6 1/. DA 00 United States Patent 3,146,767 HYDRAULIC TAPPET Morris V. Dadd, Muskegon, Mich, assignor to Johnson Products, Inc., Muskegon, Mich., a corporation of Michigan Filed May 16, 1963, Ser. No. 281,067 Claims. ((11. 123-90) This invention relates to a hydraulic lash adjustment means for internal combustion engines and more particularly to an economical hydraulic tappet, push rod, and rocker arm assembly for internal combustion engines.

In some types of internal combustion engines, the mechanisms for actuating the poppet valve comprises a valve train of several operatively connected parts which transfer motion from the eccentric cam to the poppet valve. Frequently, this valve train comprises a rocker arm, a push rod, and a hydraulic tappet which is provided for automatically adjusting the clearances between the parts of the train which vary to a considerable extent because of temperature variations and wear. The hydraulic tappet operates in a well-known manner by means of the engine oil. In some cases the oil is fed to the hydraulic tappet by means of a gallery in the engine block. In other engines, as disclosed by the Purchas, In, et al. patent, United States Patent No. 2,667,149 the oil is fed to the hydraulic tappet from the rocker arm shaft through the push rod. Although hydraulic lash adjusters of these two types are well-known, there has been considerable work done in the hydraulic tappet industry to reduce the cost of the hydraulic tappet without loss of quality or performance. Further, tremendous eiforts have been expended in attempting to improve the performance of hydraulic tappets. This invention accomplishes both the reduction of cost and the improvement of performance.

Specifically, the object of this invention is to provide a novel design of a valve train in an internal combustion engine, this valve train including a novel hydraulic tappet which is less expensive than present tappets and has the added advantage of eliminating the need of a gallery in the engine block. This novel valve train also lends itself to a shorter tappet assembly thus reducing the overall cost of the tappet. It also eliminates the varnish buildup normally occurring in present day tappets, thus eliminating the possibilities of the plunger sticking as the result of such varnish build-up. This invention also provides a larger oil reservoir which is necessary to feed the hydraulic tappet when the supply of oil from the oil pump is temporarily stopped.

This invention also provides a novel means of bleeding the air from the oil so that the oil supply to the tappet is substantially solid oil void of air which will cause the tappets to function more effectively.

These objects and advantages of this invention will become more obvious and better understood from the following description of the invention which is made in conjunction with the accompanying drawings wherein:

FIG. 1 is a transverse sectional view of a fragmentary portion of an internal combustion engine showing a portion of one of the engine valves and its valve train which includes the rocker arm assembly, the push rod, and the tappet;

FIG. 2 is a fragmentary cross-sectional view of a modified connection between the rocker arm and the push rod. This view illustrates a modified way of bleeding the air from the oil; and

FIG. 3 is still another fragmentary cross-sectional view of the connection between the push rod and rocker arm showing still another way of bleeding the air from the oil.

Briefly, this invention relates to an engine having a valve means actuated by a valve train including a rocker 3,146,767 Patented Sept. 1, 1964 "ice arm assembly, a push rod and a hydraulic tappet. A source of oil is provided in the shaft of the rocker arm assembly and this source is connected to the hollow push rod through passageways in the rocker arm. The tappet has a compression chamber communicating directly with the passageway of the push rod whereby the compression chamber is supplied by oil from the rocker arm source directly and from the push rod without passing through the normal reservoir provided in conventional present day tappets. As a result the push rod passageway serves as a reservoir for supplying oil to the compression chamber when the supply of oil from the source is temporarily stopped.

Referring now to the drawings:

FIG. 1 discloses a part of the engine valve which comprises the stem 1 and the valve spring 2 which normally holds the valve closed in a well known manner (not shown). A rocker arm assembly 10 is provided for actuating the engine valve. This rocker arm in turn is actuated by the cam 31 of the cam shaft 30 through the tappet 40 and the push rod 20. The valve train in this instance is thus considered to be the rocker arm assembly 10, push rod 20, and the hydraulic tappet 40. The hydraulic tappet, as is well known, compensates for operating clearances between the other parts which are generally due to temperature variations and wear. The rocker arm assembly comprises the rocker arm 11 rotatably or pivotally mounted on the rocker arm shaft 12 and having the actuator end 13 engaging the engine valve and the actuated end 14 engaging the push rod 20. As will be noted the rocker arm shaft 12 is hollow for the purpose of providing a source of oil. In other words, oil under pressure is present in the rocker arm shaft 12. Provided in the walls of rocker arm shaft 12 is an oil feed hole 15 communicating or aligned in at least one position of the rocker arm with an oil feed passage 16 provided in the rocker arm. An air bleed hole 17 is formed in the rocker arm shaft and an air bleed passage 18 is formed in the rocker arm 11. The air bleed hole 17 and air bleed passage 18 are offset from each other for the purpose of preventing large quantities of the oil from being forced therethrough which eliminates excessive loss of oil and resultant flooding of the overhead. The diametral clearance between the GB. of the rocker arm shaft 12 and the ID. of the rocker arm 11 provides a restricted passageway between the holes. This passageway allows the air to bleed off the top of the rocker arm shaft and also permits a small amount of oil to pass therethrough sufiicient to lubricate the rocker arm end 13 and the tip of the valve stem 1.

The actuated end 14 of the rocker arm has a push rod seat surface 19 in which the push rod 20 is seated. The push rod 20 is a hollow member so as to provide a cavity or reservoir 21 therein. At the top of the push rod an upper oil feed opening 22 is provided to communicate or align with the oil feed passage 16 which extends to the push rod seat surface 19. As a result, oil forced through the rocker arm shaft 12 passes into the reservoir or cavity 21 of the push rod. At the lower end of the push rod is provided a lower feed opening 23.

The lower end of the push rod 20 is received in a novel tappet that does not have the usual reservoir chamber. This tappet 40 comprises a tappet body 41 having a bore 42 with an open end 43 and a closed end 44. As shown this body is reciprocally mounted in a cylindrical opening 3 in the engine block 4. The closed end 44 engages the cam 31. The open end 43 receives the plunger 45 which is reciprocally mounted in the bore 42. Plunger 45 has a close fit within the bore thereby forming a compression chamber 46 between the closed end 44 and the plunger. Plunger 45 is cup-shaped providing a cavity 47 communicating with the compression chamber 46 by means of the oil feed passageway 48 which is closed off by a check valve 49 mounted within a valve cage 50. Valve 49 is normally held closed by the check valve spring 51 which operates in a well known fashion by permitting oil to pass into the compression chamber. The entire plunger is forced upwardly by the plunger spring 52.

The hollow push rod 20 extends into the cavity 47 of the plunger and its lower end seats directly against the bottom surface thereof and in sealed relationship thereto with its lower oil feed opening 23 in register with the oil feed passageway 48. As a result, oil is fed through passageway 48 and into the compression chamber 46 directly from the push rod cavity 21. Consequently, the push rod cavity 21 serves as the reservoir which, when the supply of oil from the normal oil source is temporarily stopped, supplies oil to the compression chamber. This eliminates the necessity of a separate push rod seat and also the necessity for an oil gallery in the engine block.

Assembly The assembly of this apparatus should be evident from the above description. Briefly, the tappet is first assembled by placing the check valve 49, check valve spring 51, and valve cage 50 over the lower end of the plunger 45. Then the plunger spring 52 is placed within the bore 42 after which the plunger 45 with the valve and cage on is inserted in bore 42 over the spring 52. Next, the retaining ring 53 is inserted in the groove 54 at the top of the tappet body for preventing the plunger from coming out of the bore.

The assembled tappet is placed within the cylindrical opening 3 in the engine block 4. The rocker arm assembly is assembled by merely placing the rocker arm 11 on the rocker arm shaft 12 in a position Where the actuator end 13 contacts the engine valve stem 1.

Having completed the assembly of the rocker arm assembly and the tappet within the engine block, the push rod is then inserted into the cavity 47 of the plunger 45 and into the push rod seat surface 19. Such assembly automatically determines the positions of the various oil feed and air bleed holes, passages and openings. It should be understood that the position of the oil feed and air bleed holes, passages and openings can be varied to suit the particular application so as to provide oil feed and air bleed at various intervals or times during the operation of the valve.

Operation The operation of this invention should also be obvious from the above description of the various elements and their assembly. Briefly, however, it should be understod that oil is supplied through the hollow rocker arm shaft 12. This oil is generally under pressure particularly during the operation of the engine. Before the oil is supplied to the push rod, air is bled from it through the air bleed holes 17, the air bleed passage 18 and the diametral clearance between the CD. of the rocker arm shaft and the ID. of the rocker arm. This passageway allows the air to bleed oif the top of the rocker arm shaft and also permits sufficient oil to pass therethrough for lubricating the valve stem and actuator end 13 of the rocker arm. In any event the oil fed to the tappet is solid oil void of air.

This solid oil is fed through the oil feed hole 15, oil feed passage 16, upper oil feed opening 22 and into the reservoir 21 formed in the push rod. From the reservoir 21 the oil is supplied to the compression chamber 46 through the check valve 49. Such supply takes place when the pressure within the compression chamber is less than the pressure within the reservoir 21, this usually occurring when the valve 1 is in closed position and it is necessary to take up any slack or lash in the valve train.

With this invention a large reservoir is provided in the push rod for supplying oil to the compression chamber when the supply of oil from the rocker arm shaft is temporarily stopped. This invention also eliminates the necessity for any push rod seat which usually is a separate element inserted and mounted in the top of the plunger so as to provide a reservoir within the plunger itself.

It should be obvious that this invention lends itself to a much shorter tappet assembly than was previously practical. Furthermore, this invention is automatically free from any varnish build-up surfaces that would cause plunger sticking.

Modifications FIG. 2 shows a modification for bleeding the air from the oil. This comprises rearranging the oil feed passage in the rocker arm so that it is slightly offset from the push rod. Further, the push rod seat surface has a bleed groove that registers with the hole in the upper end of the push rod providing a passageway through which the air can pass. This construction provides an air bleed while the engine valve is in closed position as shown in full line. The oil feed passage 16a registers with the upper oil feed opening 22 when the engine valve is open (phantom line). An optional air bleed is shown by a small hole 196 in the upper portion of push rod 20.

FIG. 3 shows still another modification for bleeding air from the oil. This modification provides a push rod having an upper portion cupped or funnel shaped and positioned to receive oil from the modified oil feed passage 16b. The cup-shaped portion 6 and the outlet of the oil feed passage 1612 are spaced so that oil is fed from the outlet of passage 16b to the cup-shaped portion by gravity. Thus all air in the oil is removed prior to the oil passing into the reservoir 21 within the push rod.

Having disclosed my invention, it should be obvious that although I have shown preferred forms and modifications of this invention, the protection afforded by this patent should not be limited thereto unless expressly set forth in the appended claims.

I claim:

1. In an engine having a valve means actuated by a valve train including a rocker arm assembly, a push rod and a hydraulic tappet comprising: said rocker arm assembly having a source of oil; said push rod having a passageway therethrough communicating with said source of oil; said tappet having a body with an internal bore and a closed end and an open end, a plunger reciprocally mounted within said bore, said plunger including a bottom wall having an opening therein, said wall forming between it and said closed end a compression chamber; said push rod extending through said open end and directly engaging said bottom wall of said plunger; a check valve in said opening; said passageway of said push rod being axially aligned and located over said opening providing direct communication between said passageway and said opening whereby said compression chamber is supplied by oil from said rocker arm source of oil directly through and from said push rod; said push rod passageway serving as a reservoir for supplying oil to said compression chamber when the supply of oil from said source is temporarily stopped.

2. In an engine having a valve means actuated by a valve train including a rocker arm assembly, a push rod and a hydraulic tappet comprising: said rocker arm assembly having a source of oil; said push rod having a passageway therethrough communicating with said source of oil; said tappet having a body with an internal bore and a closed end and an open end, a plunger reciprocally mounted within said bore and forming between it and said closed end a compression chamber; said plunger being cup-shaped providing a bottom wall and sides defining a cavity therein facing the open end of said body; an opening in said bottom wall of said plunger, said opening being arranged axially of said bore and having a check valve; said push rod being seated in said cavity on said wall with its passageway located over said opening thereby providing direct communication between said passageway and said opening whereby said compression chamber is supplied by oil from said rocker arm source of oil directly through and from said push rod; said push rod passageway serving as a reservoir for supplying oil to said compression chamber when the supply of oil from said source is temporarily stopped.

3. The device of claim 1 in which an air bleed means is formed at the juncture between the rocker arm and the push rod.

4. The device of claim 1 in which an air bleed means is formed at the juncture between the rocker arm and the push rod, said air bleed means comprising a space between a passageway through said rocker arm and the passageway in said push rod.

5. The device of claim 1 in which a passageway in the rocker arm connects the source of oil with the passageway in the push rod; and an air bleed means is formed by a space between the push rod and rocker arm, said space communicating with at least one of the passageways through said push rod or rocker arm.

References Cited in the file of this patent UNITED STATES PATENTS 1,792,836 Handwerker Feb. 17, 1931 2,145,484 Johnson Jan. 31, 1939 2,667,149 Purchas et a1. Jan. 26, 1954 2,676,579 Gerner Apr. 27, 1954 2,681,644 Purchas et a1 June 22, 1954 2,724,373 Dolza Nov. 22, 1955 2,739,580 Brown Mar. 27, 1956 2,937,632 Voorhies May 24, 1960 3,048,156 Van Slooten Aug. 7, 1962 

1. IN AN ENGINE HAVING A VALVE MEANS ACTUATED BY A VALVE TRAIN INCLUDING A ROCKER ARM ASSEMBLY, A PUSH ROD AND A HYDRAULIC TAPPET COMPRISING: SAID ROCKER ARM ASSEMBLY HAVING A SOURCE OF OIL; SAID PUSH ROD HAVING A PASSAGEWAY THERETHROUGH COMMUNICATING WITH SAID SOURCE OF OIL; SAID TAPPET HAVING A BODY WITH AN INTERNAL BORE AND A CLOSED END AND AN OPEN END, A PLUNGER RECIPROCALLY MOUNTED WITHIN SAID BORE, SAID PLUNGER INCLUDING A BOTTOM WALL HAVING AN OPENING THEREIN, SAID WALL FORMING BETWEEN IT AND SAID CLOSED END A COMPRESSION CHAMBER; SAID PUSH ROD EXTENDING THROUGH SAID OPEN END AND DIRECTLY ENGAGING SAID BOTTOM WALL OF SAID PLUNGER; A CHECK VALVE IN SAID OPENING; SAID PASSAGEWAY OF SAID PUSH ROD BEING AXIALLY ALIGNED AND LOCATED OVER SAID OPENING PROVIDING DIRECT COMMUNICATION BETWEEN SAID PASSAGEWAY AND SAID OPENING WHEREBY SAID COMPRESSION CHAMBER IS SUPPLIED BY OIL FROM SAID ROCKER ARM SOURCE OF OIL DIRECTLY THROUGH AND FROM SAID PUSH ROD; SAID PUSH ROD PASSAGEWAY SERVING AS A RESERVOIR FOR SUPPLYING OIL TO SAID COMPRESSION CHAMBER WHEN THE SUPPLY OF OIL FROM SAID SOURCE IS TEMPORARILY STOPPED. 